A wide variety of novelty yarns have been produced from synthetic fibers, cotton, and other natural fibers. However novelty yarns with short duration irregularities (yarn slubs), of about one inch to four inches in length, have not heretofore been made on open-end spinning equipment because of the very high speed of the spinning rotors (40,000-80,000 rpm), which produce yarn at speeds of 4,000-8,000 inches per minute. This requires making a feed change at 1/66th of second, which has not been physically possible. However, according to the present invention it is now possible to make short duration yarn slubs from cotton fibers on open-end spinning equipment.
According to the present invention, merely by providing a particular configuration of a combing roll, which delivers fibers to the rotors of an open-end spinning machine, it is possible to make novelty yarn. In fact, it has been found that by using conventional combing rollers which are typically employed for smooth synthetic fibers, such as polyester, the desired yarns according to the invention can be produced. Such combing rolls have negative tooth angles, and according to the invention it has been found that negative angles of about 0.01.degree.-15.degree. are particularly effective. Such rolls have heretofore been considered to be highly undesirable for use with cotton. For example, in an article in the Textile Research Journal by Simpson and Murray, September, 1979, pages 506 to 512, a study was made with open-end combing rolls by varying the combing wire front angle for open-end spinning of cotton between 0.degree. and +30.degree.. The poorest results were obtained at 0.degree. and at +30.degree., providing a classic indication that negative angle combing rolls have conventionally been considered to be undesirable in the manufacture of cotton yarns.
The cotton yarn produced according to the invention has typical irregularity (slub) lengths of about one half inch--four inch, normally about one half--two inches. While such yarns have a wide variety of uses, they have been found to be particularly suited for the manufacture of denim fabric. The denim fabric produced from yarns according to the invention has a different look than denim fabrics made by other processes, which is achieved by surface abrading the fabric after construction to remove dye from the surface of the slubs, emphasizing them. The yarns according to the invention may be utilized to make a wide variety of denim fabrics, that are particularly useful when the yarn and weave of the denim are selected to provide a tight construction, which highlights the slubs.
According to a first aspect of the present invention, a method of open-end spinning cotton novelty yarn utilizing a negative wire combing roll is provided. The method comprises the following steps: (a) Separating cotton sliver into cotton fibers. (b) Acting on the cotton fibers with a negative wire combing roll so that the fibers build up on the teeth of the combing roll and slide away to produce non-uniform bundles of fibers. And, (c) twisting the cotton fibers into cotton novelty yarn, having irregularly spaced (i.e. not in a pattern) irregularities each about one-half inch to four inches in length. Steps (a) through (c) are typically practiced with a twist multiple between about 3.5 TM and and 9.5% TM, with a yarn count between about 4.5/l and 20/l. (e.g. 15/l) Ne, and produce irregularities within the range of one per every thirty inches to one per every one hundred twenty inches of yarn.
When denim fabric is to be made from the yarn according to the invention, it is utilized to construct a warp of about 54-100 ends per inch (e.g. about 54-78 ends), and the warp is dyed by ring dyeing or some other method by which the core of the yarn remains white. The warp is woven with a filling yarn to produce the denim fabric.
The filling yarn is typically selected from the group consisting essentially of cotton novelty yarn, plain open-end cotton yarn, and ring spun cotton yarn, typically having a size of about 4.5/l to 12/l Ne, and about 30-70 picks per inch. The weave may be plain (1.times.1), twill (2.times.1), warp face sateen, or 3.times.1 or 4.times.1 in left hand and right hand twill constructions. The weave is tight so as to highlight the slubs more than a loose weave.
After weaving the fabric, it is subjected to surface abrasion. Typical surface abrading techniques would be stonewashing after the fabric is formed into a garment, or sanding the fabric--prior to garment manufacture--with sandpaper having a grit of about 40-300. These surface abrading techniques remove the surface of the dye on the slub yarn to show a white or lighter slub than the body of the fabric. The fabric weight typically is about 5 oz.-17 oz. per sq. yd., and typically about 50 irregularities (slubs) are provided in a six inch square, providing a unique and desirable affect in the final denim product.
It is the primary object of the present invention to produce cotton novelty yarn having short duration yarn irregularities, and/or to produce fabrics with an unusual construction utilizing such yarn. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.